PBSI 235 Exam 1

What are the fundamental information processing unit of the nervous system

Neurons (nerve cells)

What is the function of the nucleus?

It houses DNA, what genes are essentially made of

Explain the central dogma of biology

It’s a theory of the flow of genetic processing:

(DNA is copied to DNA during replication, then) DNA is transcribed to → RNA is translated to → PROTEIN

List the specialized structures for the electrical and chemical communication

Dendrite: (greek dendron meaning tree) Receive the chemical signals from other axon terminals from other neurons via dendrites and dendritic spines (allow for more surface area and more input) and convert this into an electrical signal

Soma/Cell Body: Integrates/combines information from the dendrites by summing electrical signals that are generated there. Regulates cell function with the genetic info contained in the nucleus

Axon: nerve fiber, beginning at the axon hillock or initial segment that connects to the soma, that generates a special electrical signal called the action potential that's conducted down the axon to the terminals, may branch into axon collaterals (branches) then into terminals

Axon Terminals: make contact with dendrites from other neurons by releasing a chemical due to the action potential being passed down to the axon terminal, which the electrical signal it receives thus turns into a chemical signal. They also make contact with other cell types outside of brain and spinal cord like the muscles, glands etc.)

• They contain synaptic vesicles that contain neurotransmitters; these vesicles dock at the inside of the presynaptic membrane

Describe how information flows WITHIN neurons. What type of signal is used?

Electrical signals carried from dendrites/soma down the axon to its terminals

Describe how information flows BETWEEN neurons. What type of signal is used?

Chemical signals are released from axon terminals out to the dendrites of other neurons

What is the synapse? Describe each of its parts.

Synapses are the connections between the axon terminal and the next neuron’s dendrites

• Presynaptic membrane: part of the axon terminal that releases a chemical, known as a neurotransmitter, that is received by the next cell

• Synaptic cleft: the space between the post and presynaptic membranes

• Postsynaptic membrane: part of the dendrites of the target cell (if a neuron) that's designed to receive messages in the form of neurotransmitters

What happens when an action potential arrives at the synaptic cleft?

as the electrical signal (action potential) arrives at the axon terminal, the vesicles rupture, releasing neurotransmitters (chemical signal) into the synaptic cleft, which is received through the receptor of the postsynaptic membrane that neurotransmitters bind to

What is the neuron doctrine?

Essentially is that the brain is composed of neurons

Santiago Ramon y Cajal proposed the neuron doctrine that states:

• Individual cells (neurons) are the functional unit of the nervous system

• Information flows across neurons in one direction (dendrite→soma→axon→axon terminal)

• Neurons communicate with other cells at the synapse

How did the Golgi stain contribute to Cajal’s work?

the golgi stain completely fills a small percentage of neurons allowing us to see their structures, and allowing cajal to formulate the neuron doctrine/drawings.

What is the reticulum theory?

golgi believed that the brain was not made up of cells but like a giant net (reticulum) with no synapses, no spaces between cells, no individual units within the brain

• even though it’s not the case, comb jellies were discovered to have a fused nervous system without synaptic clefts between neurons

Describe the role of glia

Glia (Greek meaning glue) support neurons in the form of nutrients, raw materials, protection, and general upkeep. They hold the nervous system together, and neurons would not be able to perform their information-processing function without them.

What is myelin?

within the brain and spinal cord oligodendrocytes create a fatty sheath, known as the myelin that wraps around the axons of neurons

• it insulates the axon and causes it to conduct the action potential more quickly and efficiently ( think like heat makes it goes faster)

Compare and contrast oligodendrocytes and Schwann cells

oligodendrocytes: the cells that create the fatty sheath (myelin) that wraps around axons in the CNS (central nervous system; brain and spinal cord neurons) of brain and spinal cord neurons

Schwann cell: creates myelin around neurons in the PNS (peripheral nervous system; cells outside the brain and spinal cord)

• they both insulate the axon to conduct action potential more quickly!

• they differ in location, etc.

What are astrocytes?

star-shaped cells with many arms that contact neurons and other cells (including the cells that make up the blood vessels of the brain)

• these arms that make contact with the blood vessels make part of the blood-brain barrier

astrocytes help convey vital nutrients from the blood to neurons

What is the role of the blood brain barrier?

the blood brain barrier is a boundary that separates the circulatory system in order to regulate what enters and to protect against pathogens

• its basically like a filter/gatekeeper to protect, maintain stbaility, and deliver nutrients

What are microglia?

Since the brain and spinal cord have no immune system, microglia help to defend the brain by scavenging these pathogens, bacteria, damaged cells, and debris

• they have a resting state where their cell bodies remain still while their arms move around to scan the surrounding area

• if a threat is detected, then they switch to their reactive state by changing their shape and moving to where they need to engulf or destroy the debris/invader

anterior

facing towards

posterior

facing away

superior

top

inferior

bottom

medial

center

lateral

outer

ipisilateral

same side

contralateral

opposite sides

dorsal

back

ventral

stomach

coronal

vertical plane that divides body into ventral and dorsal/ posterior and anterior

sagittal

plane that divides between left and right parts of body

horizontal

plane that divides body into superior and inferior

What is the theory of localization? How did these lead to phrenology? Why is phrenology considered a pseudoscience?

The theory of localization by Franz Joseph Gall states that different parts of the brain carry out separate and distinct psychological functions

• this is basically true; however, others ran with it and created the pseudoscience of phrenology

  • pseudoscience: a claim, belief, or theory that is claimed as “scientific” but does not follow the scientific method

  • phrenology: claim that a person’s personality traits, mental abilities, and behaviors could be determined and reflected by the shape and bumps of their skull (proven to be FALSE)

• it was led to phrenology because the skull wrapped around the brain, leading people to believe in phrenology

• Phrenology is considered a pseudoscience because it is FALSE

What is the contemporary perspective on localization?

that distinct psychological processes arise from the interaction of complex systems and circuits of neurons instead of being controlled by specific centers (like in phrenology)

What is a neural system?

its a population of neurons that essentially communicate across boundaries between brain regions

What is a neural circuit?

population of neurons that communicate within a brain region or between immediately adjacent brain regions

What are the basic components of the PNS?

consists of nerves and ganglia (sinlgular ganglion) outside of CNS (brain and spinal cord)

• basically everything outside of brain and spinal cord

What is the role of motor nerves?

they control muscles, so they conduct information away (efferent) from the brain and spinal cord

What is the role of sensory neves?

they convey information from the peripheral (and sensory receptors) of the body to the CNS, meaning that they conduct information toward (afferent) the brain and spinal cord

What is the role of spinal nerves? Where do they emerge from? How many pairs are there?

their role is containing sensory info about touch, the position of limbs in space etc., they also enter the dorsal (back) side of the spinal cord

• emerging from spinal cord

• theres 31 pairs

contain dorsal root ganglia

What is the role of cranial nerves? Where do they emerge from? How many pairs are there?

convey sensory info about touch, vision, taste, smell, hearing, balance, etc. into the brain

theres no clean separation between where the sensory and motor informtion enters and exits the brain

they also control the muscles of the neck and head

• they emerge from the base of the brain and there’s 12 pairs

Describe the roles of the two divisions of the PNS.

Somatic: nerves that connect CNS to the sensory and skeletal muscles

• motor/sensory nerves

• cranial/spinal nerves

Autnomic: nerves that connect CNS to the organs

What are dorsal root ganglia?

they are the cell bodies of specialized neurons that conduct sensory infor from periphery to the CNS (part of spinal nerves)

• they are like the cluster of the sensory neurons

Where does motor information going to the skeletal muscles exit from?

ventral side of the spinal cord

• the cell bodies that give rise to these axons are clusteres into nuclei in the ventral spine

Describe the two parts of the autonomic nervous system. Do they work together?

sympathetic nervous system (SNS): flight or fight response, when active, tells your organs and tissues to burn metabolic energy

• sympathetic chain ganglia: contain cell bodies of neurons whose axons form nerves that contact organs, muscles, and glands throughout body

parasympatheic nervous system (pNS): rest and digest response, tells your organs and tissues to build up and conserve metabolic energy

• parasympathetic ganglia: scattered throughout body unike chain symp, recieve input from the preganglionic neurons in the hindbrain and base of spinal cord whose axons contribute to cranial and spinal nerves

they do NOT work together, they inhibit eachother, meaning that activating one turns off the other.

What is a bundle of axons in the PNS?

nerves

What is a collection/clusters of cell bodies in the PNS CNS?

ganglia

What are the basic components of the CNS?

everything in the brain and spinal cord, encased in bone (skull and spine)

What is the role of meninges?

its a multilayered, fluid-filled sack that holds the brain and spinal cord within the skull and spine

What is cerebrospinal fluid (CSF)? Where does it come from and travel to?

one of the layers of the meninges that allows the brain to float

• originates in the ventricles (chambers of the brain)

• one-way trip starting in the brain and ending in meninges, where it gets reabsorbed into the blood

How many cerebral hemispheres is the brain divided into?

two that are mirror images of one another (think left and right form front)

What is a bundle of axons in the CNS?

tract

What is a collection of cell bodies in the CNS?

nuclei (singular nucleus)

What are the three divisions of the CNS? What makes them up?

forebrain:

• basal ganglia, cortex, limbic system, thalamus, and hypothalamus

midbrain

hindbrain:

• cerebellum

• pons

• medulla

What are the basal ganglia? Where are they located?

title is minomer, technically they are nuclei but we call them ganglia

• located deep within forebrain beneath the cortex

• critical for the intiation of voluntary motion

What is the role of the limbic system? What are its structures and their functions?

interconnected group of structures that are important for the functions of emotions and memeory

• medial temporal lobe structure:

  • hippocampus: area that is crucial for the ability to remember events

  • amygdala: area crucial for emotion and emotional memory

Compare and contrast the thalamus and hypothalamus?

• thalamus: cluster of nuclei at the CENTER of the forebrain and directs sensory info to the cortex

• hypothalamus: cluster of nuclei with many functions, such as energy intake and control of the endocrine (hormonal) system via pituitary gland

what is the pituitary gland?

the so-called master gland of the body, controllign hormone production

What is the cortex? Where is it located?

the wrinkly exterior in the human brain, contributes to everything from perception to decision making

What are gyri? What are sulci?

• gyri are the “hills” of the wrinkles (singular gyrus)

• sulci are the valleys of the wrinkles (signular sulcus)

Compare and Contrast white and gray matter

gray matter is surface of cortex, made of cell bodies, dendrites, and UNmylienated axons

white matter is inside part, made of axons covered in myelin that arose from cell bodies in gray matter

Describe the functions of 4 cortical lobes

frontal: decision, attention, planning motor control etc.

parietal: touch, propropception (position of limbs in space)

occipital: vision

temporal: hearing

What is the cortical surface made up of?

GRAY MATTER

90% neocortex (humans): 6 disctinct layers of cells, layer 1 is superficial and layer VI is deepest

10% allocortex (humans): 3/4 layers of cells depending on region (ex. piriform cortex is 4 layers at the base of temporal lobe)

What type of brain has a smooth cortex?

Lissence brains (rats and rabbits etc.)

What type of brain has a wrinkly cortex?

gyrencephalic brains (humans, chimpanzees etc.) more gyri is more surface area and more cortical cells

What is the ventral midbrain called? WHat is its function?

tegmentum, and it is the home to cell bodies that send axons to basal ganglia and cortex, releasing the neurotransmitter dopamine onto neurons in those areas

What is the dorsal midbrain called? What is its function?

tectum, and it processes the visual and audio information, as well as controlling orientation processes.

What is the medulla? What does it contain?

outgrowth of spinal cord, contains nuclei that gives rise to cranial nerves

What is the pons? What does it contain?

connects the rest of brain to the cerebellum, and it contains nuclei that gives rise to cranial nerves

What is the cerebellum?

crucial for precision control of motion

What must all sensory information coming in from and motor information going out of spinal cord pass through?

pons and medulla

What are the postsynaptic potentials? Where are they located in a neuron?

at dendrites and soma: input of chemical signals from other cells causes local changes in electrical charge

What is an action potential and how is it generated?

if changes are big enough to raise voltage at intial segment (axon hillock) beyond threshold, then action potential is generated and is conducted down axon

an electrical signal

Describe the all or nothing principle

either a complete response or total lack of response/effect depending on the stimulus

Describe resting potential

at rest, neuron has negative electrical charge relative to the outside (ranes from -50 to -80mV)

What are the electrical properties of a neuron due to?

ion gradient and the movement of ions across the cellular membrane

what are ion channels? List and describe three types

proteins that span the membrane and allow ions to pass through from one side to the other (ions can’t pass through membranes without these channels)

• selective/semi-selective

• gated

• constantly open

NAme and describe two forces that determine whether an ion channel will permit ions or enter or exit the neuron

diffusion (chemical pressure): particles will tend to move from more concentrated to less concentrated areas until they are im uniform

Electrostatic: causes ions to move away from similar charge and towards opposite charge (voltage is a measure of potential for this)

what is the sodium/potassium pump? What does it pump into/out of the cell and what powers these exchanges? Is the pump always active?

pump pulls 2 K (potassium) into cell for every 3 Na (sodium) ions it removes from the cell.

one molecule of ATP to power the exchanges

yes pump is constantly active

when is the potassium gradient at equilibrium?

resting potential

define hyperpolarization. When does it occur?

when the charge inside neuron becomes more negative

• when neg charges ions enter or pos ones leave

define depolarization. when does it occur?

inside neuron gets more positive

• when pos charge neurons enter or neg ones leave

What are ionotropic receptors? how do they impact signals. give example and where it gets its name from.

they are ion channels that open when neurotransmitters bind to them

• converts chemical to electrical signals

• in the postsynaptic membrane

• ex. nicotinic acetylcholine receptor:

• gets its name from the fact that nicotine binds to receptor and opens mimicking the action of acetylcholine

describe differences between excitatory postsynaptic potentials and inhibitory postsynaptic potentials. Are they graded? Do they last long over time and distance?

excitatory where iontropic receptors allow positice charges ions in neuron causing depolarization

inhibitory where iontropic receptors allow neg charges into neuron causing hyperpolarization around synapse

they are graded, size and duration varies depending on amount of neurotransmitter released

diminsh quickly

define spatial summation

summation is neg and pos being added together

combining influence of postsynaptic potentials (PSPs) across space. the closer they occur in space more likely to sum together

define temporal summation

combining influence of postsynaptic potentials (PSPs) across time. the closer they occur in time more likely to sum together

how does rising phase of action potential occur

voltage-gated sodium channels open to allow Na+ ions into the axon

when are voltage-gated sodium channels open? when are they closed?

when the voltage on the interior of axon is between threshold around +40mV when they reach high end of range they close and stop letting Na+ into axon

what happens during the falling phase (rapid hyperpolarization) of the action potential?

the charge inside axons returns to normal resting potential (after briefly dipping below it)

how are voltage-gated potassium channels opened?

when the pos charge that occurs during rising phase (rapid depolarization) opens voltage-gated potassium channels

What is the refractory period? can the action potential travel in multiple different directions?

after the channels opened nd close they enter refractionary period where they will not open again, cruicial

action potential only travels in one direction

can the speed of action potentials vary between neurons? within a neuron?

speed can vary between neurons but not within neuron has to be constant

what generates the action potential in a myelinated axon?

nodes of ranvier, the gaps in the myelin

define saltatory conduction.

how action potential jumps from node to node of myelinated axon

what can happen when myelin is damaged?

loss of myelin can be detrimental

• without insulation provided, the diffusion of Na+ becomes less efficient, slowing the action potential or eliminating it

if a drug has -caine in its name, what does it act as? how do these influence action potential?

• local anesthetic

• all sensation is dulled bc drug temp prevents voltage-gated sodium channels from working

Explain the role of voltage-gated calcium channels. What happens to the synaptic vesicle when calcium is detected?

• open and allows ca2+ ions into terminal in response to depolarization caused by the action potential

• when calcium is detected vesicles rupture and ejects the neurotransmitter into synaptic cleft

does the brain function like a digital computer?

no

sparks vs soups debate

sparks thought synaptic communication was electrical while soup thought it was chemical lasted until 1950s

neurotransmitter

molecules that are syntheszed in presynaptic neurons and stored in axon terminals, released when action potential arrives at axon terminal

how can botulinum toxin prevent neurotransmitters from doing their job

by preventing synaptic vesicles from docking inside presynaptic memebrane, prventing neurotransmitter relaese

what does potent neurotxin from the clostridium botulinum do to synaptic vesicles?

prevents nerve endings from communicating with muscles